Notochord Differentiation in the Ascidian, Ciona Intestinalis

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0131758LevineThe focus of the proposed study is to characterize the gene regulation networks underlying notochord differentiation in a simple chordate, the ascidian Ciona intestinalis. The research plan includes three specific aims. First, the Snail repressor appears to inhibit notochord differentiation in the presumptive tail muscles. This will be tested by misexpressing both wild-type and mutant forms of the Snail protein in electroporated embryos using defined tissue-specific enhancers. Second, two different target genes of the Brachyury activator, Ezrin and Meg1, have been implicated in mediating cell shape changes during notochord differentiation. The activities of the encoded proteins will be investigated by expressing different dominant-negative forms of the proteins in the notochord. The third line of research will explore the basis of T box specificity, whereby related T-containing transcription factors control the differentiation of distinct tissues. Particular efforts will focus on Brachyury and Tbx6, which regulate distinct sets of target genes in the notochord and tail muscles, respectively.